Quite recently, David Bailey decided to make a sculpture of his old friend Andy Warhol. In his studio on Dartmoor, he took a tin can, filled it with beans and then took some more beans to sculpt into the semblance of Warhol's head. The idea was that the head would seem to spew from the tin, and the resultant sculpture was to be called Dead Andy. Bailey capped the bean head with a blue-rinsed approximation of Warhol's hairdo and covered the lot in plaster. Then, like a Nigella of sculpture, he left it to set.

"I thought I knew what I was doing," says one of the world's most illustrious photographers. "But when I got up in the morning, the thing had exploded. Total fucking disaster, plaster everywhere."

"Dried beans, the ones you soak overnight, just expand in those conditions," says Bailey's wife, Catherine.

"That's right!" says Bailey. "So I did it again it, but this time with sweets."

And, of course, they don't detonate overnight. Bailey cackles like Dudley Moore, and reaches for another fag. We're sitting on the terrace of his 13th-century farmhouse on Dartmoor, having a lovely lunch made by Catherine. She is the former model who became Bailey's fourth wife when she was 22, and he was in his early 40s (the others were Rosemary Bramble, Catherine Deneuve and Marie Helvin). From here, green hills seem to roll away for ever, or at least to Torquay. "Fucking dreadful for my asthma," complains Bailey. "It's so damp here."

So is he working hard? "Harder than ever. I'm 72, but I'm painting, sculpting, making little boxes that the art ponces call cabinets of curiosities, making photographs. I've never worked in plaster or clay before, but I'm learning. I love learning new techniques."

Bailey is certainly busier than most pensioners. He's just back from Afghanistan, where he was snapping soldiers to raise money for the Help the Heroes charity. He's putting together two books about Delhi, and expects to mount six exhibitions of his work this year. "All except painting," he adds. "They want me to put on a painting exhibition, but I said I've got enough enemies already."

He has less compunction about his sculptures. Next month, David Bailey Sculpture + opens at the Pangolin gallery in King's Cross, London. "In this exhibition," says the blurb, "Bailey strips away conventional beauty, and instead focuses on the skull that lies beneath the perfect skin once captured by his camera." You get the idea: Bailey once made Jean Shrimpton into a swinging 60s icon; he once shot the Kray brothers in their murderous pomp; he once captured the Rolling Stones' Brian Jones – but now he's turning his back on celebrity and going all David Attenborough on us.

'Yes! Yes! Yes! No. No. Yes!'

"The skull is nature's sculpture," he says. "The old ones get this lovely patina." In the exhibition, new photographs of animal skulls will hang from the walls, surrounding bronze and silver casts made from Bailey's sculpted maquettes at the gallery's foundry.

"I'm not a sculptor," he says. "I'm an image-maker. Did you know I've got an Emmy?" For what? "For a 30-second fucking commercial for cancer! It was anti-smoking and had this girl's face melting from all the tar she was smoking. A woman rang me and said, 'Are you David Bailey, the director?' And I said, 'That's debatable, love.' She said, 'You're the first non-American to win an Emmy for a commercial.' And I said, 'Does the manicurist get one too?' She got furious. I love Americans, but I'd like them more if they knew when someone's taking the piss." He stubs out his cigarette. "But the point is I just make images – the medium is secondary."

Before seeing Bailey in Dartmoor, I visit the London backroom where his sculptures are currently housed. Many of the works feature skulls, but the one that captivates me is called Adam, a circle-faced figure/assemblage that has a leering expression, and a snake for an arm reaching down to clutch a rudimentary penis. Is the snake's head pulling the putative plonker, I wonder, or biting it?

According to the catalogue essay, something else is going on: "The vaunted phallicism of the 'shooting' camera lens is invoked here." That description makes me think of David Hemmings in the 1966 movie Blow-Up, playing a version of Bailey as he shoots Vanessa Redgrave. Then it makes me think of Mike Myers as Austin Powers, snapping Ivana Humpalot, or some other satirised 60s siren, to this monologue: "Crazy baby. Give me some shoulder. Yes! Yes! Yes! No. No. Yes! And – done. Here you go, luv. I'm spent." Before chucking the camera, post-coitally, over his shoulder. Vaunted phallicism indeed.

You've got a nerve showing sculptures in King's Cross, I tell Bailey. He looks at me blankly. Round the corner at the Gagosian Gallery, there is Picasso's Mediterranean Years, a show featuring assemblages and sculptures to which the photographer clearly owes a debt. One of Bailey's sculptures, called Pretty Woman, is an oil can with a long spout perched on gangly bird's legs. It looks like a knock-off of one of those Picasso assemblages (a pregnant goat with an exhaust pipe for an anus, for instance).

"I've always been an image-maker, and now I'm making images that aren't photographs," says Bailey. Fair enough, but the "now" is misleading. Even when he was a little East End scruff, bunking off school, breeding parrots and going on ornithological rambles, he was already an artist, making shoebox-sized cabinets of curiosities like Joseph Cornell's. "I didn't know it was art, but I was always making boxes. I'd call them things like Stone I Found in Forest Gate."

He still makes boxes, with broader ambitions. After lunch, he shows me several, one of which is called America and includes a Confederate flag, a severed green baby's head and a Mexican stick figure. "It's about America – abortion, immigration, you know," he says.

Bailey was born in 1938 in Leytonstone, London, a couple of streets from Hitchcock's birthplace, and later moved to East Ham. "The only form of art in the East End was the movies. We would go to the pictures with bread and jam sandwiches five or six nights a week to keep warm – it was cheaper than putting on the heating at home, so I saw a lot of films." In his studio, he shows me a heartfelt painting of Hitler with Mickey Mouse, bearing the caption: "1944 Hitler killed Mickey in Upton Park." Nearly 70 years on, what the Luftwaffe did to six-year-old David still wrankles. "Hitler bombed Upton Park cinema. I thought he'd killed Mickey and Bambi, the cunt."

Disney wasn't little David's only cultural infusion. "I saw a Picasso in Look magazine when I was 17. I didn't know what art was before then, and it blew me away. If there's ever been a bit of revelation in my life, that was it. Picasso showed me there were no rules. A bicycle wheel doesn't have to be round. He had a simple visual inventiveness, never complicated and never pretentious. That's what my photographs are about – keeping it simple.

"That's why I like primitive art. And that's why I like the blues, which is the only great art form to have come out of America – and it's really African. Some of those guys only knew four songs. But so what? Express yourself. Keep it simple."

Four weeks with cannibals

Despite his interest in art, Bailey never went to art school. "They wouldn't have let me in with my school record, but anyway, I think it would have fucked me up." Why? "What I do is direct and simple. Not sure art school would have helped me get there." Instead, he did two years of national service in Malaya. "There's a picture of me somewhere by my bed in the jungle with a picture of Picasso over it. They would say to me, 'Who the fuck do you think you are?' But I was a cockney so I was used to fighting."

Bailey has collected art, especially tribal masks, since the early 60s. He takes me round the art in his house. "Not many photographs here because it's too damp," he says, as we breeze through the living room's display of masks. "You're the first journalist I've let in. That's rubbish. That's rubbish. That's good. I got that from New Guinea when I spent four weeks with some cannibals. That's rubbish. That's rubbish. I've got truth-telling Tourette's, you see. That's a lovely mask from Benin. That's rubbish. That's an Arp, that's Irving Penn. That's by my favourite photographer, [Manuel] Bravo."

We wander into a bedroom. "That's a dead bear," he says pointing to the pelt on the bed. "That's a dead tiger. And that," he says, pointing to a doll from the second Austin Powers film, "is little me." Bailey clearly accepts Mike Myers's back-handed tribute.

It's time to go. What will you do if the critics give your sculptures a pasting? "I don't mind if people don't like my things. I do it for myself nowadays. It's only a few nutcases who do art for themselves, like Van Gogh. But I'm not going to cut off my ear."